[rust-dev] Incremental and generational GC

Patrick Walton pwalton at mozilla.com
Thu Jul 11 11:25:23 PDT 2013

OK, after talking with Felix and Niko (thanks!) here's a proposal.

* Whenever we borrow an `@mut` to `&mut`, add it to a "borrowed set" for 
the duration of the borrow.

* Objects in the borrowed set are grayed before each incremental GC slice.

* Objects in the borrowed set are scanned during each minor collection, 
even if they're tenured.

* When removing an object from the borrowed set (because the borrowed is 
done), add it to a remembered set. Objects in the remembered set are 
scanned during minor collections.

* There are no other write barriers.

I believe (although I haven't thought about it too hard) that this 
suffices to make generational and incremental GC work in Rust's 
mostly-copying setting.


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